JPH07226355A - Exposure method and exposure apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] The focus determination can be improved by taking into consideration the actual state of the exposed material (actual wafer, etc.) to improve the focusing accuracy. Also, from the state of the exposed material (wafer) (EN) Provided are an exposure method and an exposure apparatus which can be configured to obtain an appropriate exposure amount at the time of exposure. By using the blinds 1a, 1b and the like, light is allowed to pass only through the focus mark M portion arranged on the reticle 2, whereby light having the same wavelength as the exposure wavelength is passed through the optical system to expose the exposed material 3 (actually, An exposure method and an exposure apparatus that irradiate a wafer) and determine the focus position by the reflected light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and an exposure apparatus. INDUSTRIAL APPLICABILITY The present invention can be used as, for example, an exposure method and an exposure apparatus used when manufacturing an electronic material (semiconductor device or the like).

[0002]

2. Description of the Related Art As the degree of integration of semiconductor devices increases, the level difference between patterns formed on the semiconductor devices becomes more severe.
At the time of exposure in the photolithography process for pattern formation, the focus margin does not have a margin on the actual pattern, and the pattern may not be formed due to a slight shift in focus.

A focus system of an exposure machine which has been conventionally used is shown in FIG. In this method, a preset distance d ₁ between the best-focus lens 14 and the exposure surface 30 of the exposure target wafer is input. That is, as shown in FIG.
The light beam emitted from the ED is reflected by the exposure surface 30 and enters the position detection sensor 15. From that position, the exposure surface 30 and the lens 14
The stage is moved to the best focus position by finding the distance of and adjusting it to d ₁ .

However, in this method, since the light beam does not pass through the lens 14, the state of the lens 14 cannot be taken into consideration.
The best focus is originally determined from the optimum shape of the length-measuring SEM along with the miniaturization of the pattern (the optimum shape of the photoresist PR must have the same pitch as shown in FIG. 6). Since it is indispensable, the above method eventually causes problems such as poor throughput.

On the other hand, there is a method of determining the focus by passing light through the lens using the same wavelength as the exposure wavelength. This is called TTL. This optical system is shown in FIG. The light that has passed through the reticle 2 passes through the lens 14, is reflected by the exposure surface 30, passes through the lens 14 again, and passes through the reticle 2.
Light comes back to. Since the reticle 2 and the exposure surface 30 are at optically equivalent positions, if the focus is deviated, the amount of light that can pass through the reticle 2 decreases. Therefore, the position where the light amount is maximum is the best focus position. This method can take into account the state of the lens that changes day by day because light is passing through the lens 14. It also has the advantage of good throughput.

However, since this method uses light having the same wavelength as the exposure wavelength, it is difficult to use because the pattern is exposed on the actual wafer. In addition, since the mirrors 12A and 12B are actually used as the exposure surface to reflect the light, the state of the actual wafer to be exposed (pattern, resist, base, etc.) is not reflected. Further, when the length measuring SEM is used, there is a problem that the required proper exposure amount cannot be obtained.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art. The present invention enables focus determination in consideration of the state on an actual material to be exposed (actual wafer, etc.) An object of the present invention is to provide an exposure method and an exposure apparatus which can improve the accuracy and can also be configured to obtain an appropriate exposure amount at the time of exposure from the state of a material to be exposed (wafer).

[0008]

According to the invention of claim 1 of the present application, the light is transmitted only to the focus mark portion arranged on the reticle, whereby the light having the same wavelength as the exposure wavelength is irradiated to the exposed material through the optical system. The exposure method has a structure in which the focus position is determined by the reflected light thereof, and the above-mentioned object is achieved thereby.

According to the invention of claim 2 of the present application, when exposure is performed a plurality of times, a blind is used for each exposure to pass light only to a focus portion to determine a focus position and perform exposure. The exposure method according to claim 1, wherein the above object is achieved.

According to the invention of claim 3 of the present application, light is passed through the focus mark portion arranged on the reticle, whereby light having the same wavelength as the exposure wavelength is irradiated to the material to be exposed through the optical system, and the reflected light is used. An exposure method configured to determine an appropriate focus position by obtaining a difference between a determined focus position and a focus position determined from a shape, which achieves the above object.

According to the invention of claim 4 of the present application, a blind is arranged in the optical system in such a structure that the light passes through only the focus mark portion arranged on the reticle, whereby light of the same wavelength as the exposure wavelength is transmitted through the optical system. While illuminating the exposure material and obtaining the focus position data from the reflected light, light is passed through the focus mark portion arranged on the reticle,
As a result, the light having the same wavelength as the exposure wavelength is applied to the material to be exposed through the optical system, and the difference between the focus position determined by the reflected light and the focus position determined from the shape is obtained in advance, and the data and the difference are calculated. The exposure method according to claim 3, wherein the appropriate focus position is determined from the above, and the above object is achieved thereby.

According to the invention of claim 5 of the present application, a blind is arranged in the optical system in such a structure that light passes through only the focus mark portion arranged on the reticle, whereby light of the same wavelength as the exposure wavelength is transmitted through the optical system. The exposure material is irradiated and the reflected light is passed through a photodetector, the reflectance at the base is obtained by the photodetector, and the amount of light absorbed by the substrate is obtained from this and the amount of transmission to the base. An exposure method characterized by obtaining an optimal exposure amount for pattern formation from a state,
This achieves the above object.

According to the invention of claim 6 of the present application, a blind is arranged in the optical system in such a structure that light passes only through the focus mark portion arranged on the reticle, whereby light of the same wavelength as the exposure wavelength is transmitted through the optical system. The focus position is determined by irradiating the exposure material with the reflected light, the reflected light passes through a photodetector, the reflectance at the base is obtained by the photodetector, and the resist is determined from this and the amount of transmission to the base. An exposure method characterized in that the amount of light absorbed in a substrate containing the light is determined, and the optimal amount of exposure for pattern formation is determined from the state of the substrate including this amount of light and the type of resist, thereby achieving the above object. It is a thing.

According to the invention of claim 7 of the present application, a blind is arranged in the optical system in such a structure that light passes only through the focus mark portion arranged on the reticle, whereby light of the same wavelength as the exposure wavelength is transmitted through the optical system. An exposure apparatus capable of irradiating an exposure material and deciding a focus position by the reflected light thereof, thereby achieving the above object.

According to the invention of claim 8 of the present application, when the exposure is performed a plurality of times, the focus position is determined using the blind for each exposure, and the exposure is performed.
The exposure apparatus described in (1) above achieves the above object.

According to the present invention, when the light having the same wavelength as the exposure wavelength is passed through the lens to determine the best focus, the optics before or after the reticle are arranged so that the exposure light only passes through the focus mark portion arranged on the reticle. This can be embodied as an exposure method and an exposure apparatus in which a blind is arranged in the system, and thereby the focus is determined using reflected light on an actual material to be exposed such as an actual wafer.

In addition, an element / device for increasing the amount of light (amplifying the reflected light) without changing the phase is provided in the optical system, or a light source with an increased amount of light is arranged to increase the light intensity. It can be carried out.

Further, by inputting the offset amount between the focus determined as described above and the best focus determined from the shape, exposure can be performed with the best focus.

Further, the optical system is provided with a photodetector (the optical amplifier can also function as the photodetector), the reflectance on the underlayer is obtained by this, and the substrate is absorbed from this and the amount of transmission to the underlayer. The amount of light (which is considered to be mainly the amount of light absorbed in the resist) is obtained, and the optimum amount of exposure for pattern formation is obtained from this amount of light and the type of resist or the like.

[0020]

[Operation] In the present invention, light having the same wavelength as the exposure wavelength is passed through the lens and then reflected on the actual material to be exposed (actual wafer, etc.) to show the state of the actual exposure surface such as the actual wafer. The focus can be determined by taking into consideration, so that the focus accuracy is improved. Also, the exposed surface (wafer, etc.)
The appropriate exposure amount at the time of exposure can be determined from the reflectance of the.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following examples.

Embodiment 1 This embodiment embodies the present invention as an exposure technique for resist exposure in a manufacturing process of a miniaturized and integrated semiconductor device.

The structure of this embodiment is shown in FIG. Further, as shown in FIG. 8, focusing marks M ₁ and M ₂ are arranged on the reticles 2a and 2b used in this embodiment. At this time, since the same wavelength as the exposure wavelength is used, the marks M ₁ ,
The position of M ₂ is changed and arranged for each of the reticles 2a and 2b. Depending on the coordinates of the position, the blinds 1a and 1b shown in FIG. 1 (the blind may be either 1a in front of the reticle 2 or 1b after the reticle 2).
Open only the corresponding part of the focus mark M. Focus measurement is performed in this state.

Referring to FIG. First, as shown in the figure, the light ray passes only through the portion M of the focus mark. The light passes through the lens 14, is reflected by the real wafer that is the material 3 to be exposed, passes through the lens 14, and returns to the reticle 2. In order to reflect on the exposed material 3 (wafer) actually used for exposure, information on the exposed surface (wafer surface) such as a resist and a base is also included. Further, since the other portion is covered by the blind 1a or 1b, the actual pattern portion is not exposed. Since the reticle 2 and the material to be exposed 3 (wafer) are in an optically equivalent position during the best focus, the amount of reflected light including the information about the background can pass through the reticle 2 during the best focus. The position is calculated, and it becomes the best focus position.

In this embodiment, the reflected light is more reflected by the material 3 (actual wafer) to be exposed than when it is reflected by the mirror (see TTL in FIG. 7). It is considered that the reflected light is attenuated due to unevenness or the like. Therefore, in order to secure the quantity of reflected light, a lamp having a high intensity can be separately used. That is, FIG.
As shown in (b), a main exposure light source 11a and a focus determination high-output light source 11b having a higher intensity than the main exposure light source 11a can be provided so that they can be switched. Further, it is preferable to install an optical amplifier 13 which is an element / device that electrically amplifies the intensity of the reflected light before the reflected light reaches the reticle 2. However, at this time, the phase of the reflected light is not changed.

After determining the best focus, the blind 1a
Alternatively, the entire surface of 1b is opened and main exposure is performed.

This focusing can be performed only at one point in the exposed material 3 (wafer) by opening and closing the blind only once at first.

Further, by opening and closing the blind for each shot (one exposure), it is possible to improve the accuracy more than obtaining the best focus for each shot.

According to this embodiment, the best focus can be obtained with higher throughput and accuracy than ever before.

That is, since the reflected light on the actual material to be exposed such as an actual wafer is used, the influence on the focus of the base can be taken into consideration, and the focus accuracy is improved. Further, since the reflected light on the actual material to be exposed (actual wafer) is used, the offset amount from the focus obtained from the shape does not fluctuate more than when reflected on the mirror surface, and the focus accuracy improves. In addition, since the best focus can be determined for each shot, it is preferable to determine the best focus for each shot under severe conditions. Usually, the focus can be set and implemented for one wafer. Further, according to this embodiment, the throughput up to focus determination is improved.

Example 2 According to the knowledge of the present inventor, the best focus of TTL (see FIG. 7) obtained by reflecting light with a mirror and the best focus obtained from the shape by length measuring SEM are
There is a certain offset. This example is based on this finding.

TT obtained by reflecting light with a mirror
FIG. 2 shows the offset between the best focus of L and the best focus obtained from the shape by a length measurement SEM or the like. Table 1 below shows such data. Table 1
The above data are for the case where a novolac-based resist is used.

[0033]

[Table 1]

FIG. 2 is a plot of the best focus obtained from TTL after coating a resist on Si and the focus obtained from length measuring SEM for about one month. It can be seen that it has a constant offset. The result of the offset is shown in Table 1, which shows the offset with respect to the other two types of resists.

In this embodiment, the focus can be determined by using the same method as in Embodiment 1 by using the reflection on the actual material to be exposed (actual wafer). Therefore, it is not necessary to consider the step between the material to be exposed (wafer) and the mirror, the offset amount with a small variation can be measured, and the offset amount can be determined in a short period.

By inputting the offset amount,
The focus of Example 1 can be automatically adjusted to a focus with an offset using software, and the focus accuracy can be further improved.

Embodiment 3 The configuration of this embodiment is shown in the flow chart of FIG. This example is based on the following findings by the present inventor.

The amount of light absorbed in the resist is involved in the pattern formation of the resist (the surface condition other than the resist is also considered to be involved in some degree). FIG. 3 shows the relationship between the light absorption in the resist PR and the incident light, reflected light, and transmitted light.

In this embodiment, based on the principle shown in FIG. 3, the optimum amount of light to be absorbed in the resist is calculated in advance from the exposure amount by which the base and the resist are changed to form the optimum pattern.

In this embodiment, the same optical system as that of the first embodiment is used, and when light passes through this optical system, the optical amplifier 13 (see FIG. 1) is also used as a light intensity detector, and The amount of incident light and reflected light passing through is also obtained at the same time. By determining the base, the amount of light transmitted from the resist to the base can be known. Since the amounts of incident light, reflected light, and transmitted light are known, the amount of light absorbed in the resist is known, and the ratio of the amount of light absorbed in the resist is known.

The optimum exposure amount for forming the optimum pattern can be determined from the ratio of the exposure amount and the absorption, by performing the exposure until the absorption amount is obtained in advance for each underlayer.

With the scraping method, the optimum exposure amount can be obtained with high throughput. FIG. 4 shows a flow chart of this method. That is, as shown in FIG. 4, in this embodiment, the optimum light absorption amount for pattern formation is obtained for each resist and converted into data (31a), while the light transmittance of the underlayer is measured and stored in a database. (31b).

By the optical system of the first embodiment, the measurement of the incident light and the reflected light from the photodetector (which may also serve as the optical amplification device) is polluted (32). From this measurement result and the information (31b) stored in the database, the amount of light absorbed in the resist can be known with respect to the incident light (33). Also, the ratio of the amount of absorption to the incident light is known (34). Further, the ratio of the absorption amount to the exposure amount is known (35). The optimum exposure amount can be determined for each material (wafer) to be exposed from the above and the information previously converted into data (31a) (36).

[0044]

According to the present invention, it is possible to determine the focus in consideration of the actual condition on the exposed material (actual wafer, etc.) to improve the focusing accuracy, and to improve the exposure accuracy of the exposed material (wafer). It was possible to provide an exposure method and an exposure apparatus capable of obtaining a suitable exposure amount at the time of exposure from the state.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment.

FIG. 2 is a diagram for explaining a second embodiment.

FIG. 3 is a diagram for explaining a third embodiment.

FIG. 4 is a flowchart showing a third embodiment.

FIG. 5 is a diagram showing a conventional technique.

FIG. 6 is an explanatory diagram of a resist optimum shape.

FIG. 7 is an explanatory diagram of a conventional TTL autofocus system.

FIG. 8 is a diagram showing an example of focus mark wiring on a reticle.

[Explanation of symbols]

11, 11a, 11b Light source 1a, 1b Blind 2 Reticle 3 Exposed material (actual wafer) M, M ₁ , M ₂ Focus mark

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03F 9/00 H

Claims (8)

[Claims] 1. A structure in which light is transmitted only to a focus mark portion arranged on a reticle, whereby light having the same wavelength as the exposure wavelength is irradiated onto an exposed material through an optical system, and the focus position is determined by the reflected light. The exposure method configured. 2. The exposure according to claim 1, wherein when the exposure is performed a plurality of times, the exposure is performed by determining the focus position by passing light only through the focus portion using a blind for each exposure. Method. 3. A light is passed through a focus mark portion arranged on a reticle, whereby light having the same wavelength as the exposure wavelength is applied to an exposed material through an optical system, and a focus position and shape determined by the reflected light are determined. An exposure method configured to determine an appropriate focus position by obtaining a difference from the determined focus position. 4. A blind is arranged in an optical system so that light passes through only a focus mark portion arranged on a reticle,
As a result, light with the same wavelength as the exposure wavelength is applied to the material to be exposed through the optical system, the data of the focus position is obtained from the reflected light, and the light is passed through the focus mark part placed on the reticle, which allows the exposure wavelength The difference between the focus position determined by the reflected light obtained by irradiating the exposed material with the light of the same wavelength through the optical system and the focus position determined from the shape is obtained in advance, and the appropriate focus position is determined from the data and the difference. The exposure method according to claim 3, wherein the exposure is determined. 5. A blind is arranged in an optical system so that light passes through only a focus mark portion arranged on a reticle,
As a result, the light having the same wavelength as the exposure wavelength is irradiated to the exposed material through the optical system, the reflected light is passed through the photodetector, and the reflectance at the base is obtained by the photodetector. The exposure method is characterized in that the amount of light absorbed by the substrate is obtained from the above, and the optimal exposure amount for pattern formation is obtained from this amount of light and the substrate state. 6. A blind is arranged in an optical system so that light passes only through a focus mark portion arranged on a reticle,
As a result, light having the same wavelength as the exposure wavelength is irradiated to the material to be exposed through the optical system, the focus position is determined by the reflected light, and the reflected light passes through the photodetector and is reflected by the photodetector on the base. The ratio is obtained, and the amount of light absorbed in the substrate containing the resist is obtained from this and the amount of transmission to the base, and the optimal exposure amount for pattern formation is obtained from the state of the substrate containing this amount of light and the type of resist. Exposure method. 7. A blind is arranged in an optical system so that light passes through only a focus mark portion arranged on a reticle,
This makes it possible to irradiate the material to be exposed with light having the same wavelength as the exposure wavelength through the optical system and determine the focus position by the reflected light. 8. The exposure apparatus according to claim 1, wherein when the exposure is performed a plurality of times, the exposure is performed by determining the focus position using the blind for each exposure.